I transferred school districts the summer before sixth grade. My old district did not include grammar in the curriculum until middle school. My new district covered it in elementary school. While I was able to catch up in math, due in part to some very patient teachers and my parents, I never caught up in grammar.
I desperately wanted to take a grammar class in high school, but by the time I was eligible, the class was phased out. As I was an Honors English student, the department did not listen to my pleas for this class.
To me, grammar is perfect. If you follow the rules, you are rarely wrong. I am not perfect, so having rules makes it easier for me.